There are basically two types of loupe assemblies for surgical, medical and dental professionals: (1) the flip-up type, which provides for multiple degrees of adjustment freedom, and (2) the through-the-lens (TTL) type, which offer few, if any, adjustments after manufacture and are therefore often custom made.
Whereas flip-up type loupe assemblies typically offer an interpupillary distance adjustment, TTL versions ordinarily do not. There have been attempts, however, to provide TTL loupes with such an adjustment, at least for fitting purposes. According to U.S. Pat. No. 6,799,847, for example, a sliding bridge eyeglass frame provides salespersons and customers the ability to ensure that a proper interpupillary distance between loupe oculars is achieved during a fitting session. The “demonstration frame” includes first and second bridge portions which are slidably and reversibly fixedly attached to lenses, thus allowing a customized fitting for particular customers. Once proper interpupillary distances are achieved, the first and second frame members are secured together such that proper dimensions and configurations can be obtained for production of a final product.
While devices such as these provide for pre-production adjustment, the need remains for a TTL loupe product that can be adjusted in the field, preferably with a mechanism that does not interfere with ornamental appearance and with a nose bridge.